Early fault section positioning method based on active injection

Abstract

The invention discloses an early fault section positioning method based on active injection. The method comprises the steps: firstly constructing an early fault model expression of a flexible DC system based on the early fault features of a DC cable; based on the constructed early fault model expression, utilizing active control on a DC / AC converter to actively inject disturbance current into the flexible direct current system; and according to the early fault characteristics after the disturbance current is injected, obtaining an early fault identification criterion, and making an early fault processing scheme of the flexible DC system based on the early fault identification criterion. The method can be used to accurately identify and position an early fault section, timely isolates a fault branch, has certain anti-noise capability, and provides guarantee for continuous and reliable operation of the flexible DC power distribution system.

Description

technical field [0001] The invention relates to the technical field of grid-connected new energy power generation, in particular to an early fault section location method based on active injection. Background technique [0002] In the flexible DC distribution network, due to the limited overcurrent resistance of fully-controlled power electronic devices, once a short-circuit fault occurs between poles, the converters of the whole network will be quickly blocked in a very short time, resulting in a long-term power failure of the system, which will cause great damage. Reduced system reliability. For this reason, how to solve the problem of system outage caused by DC short-circuit faults has become an urgent problem to be overcome in the protection of flexible DC distribution networks. The high-frequency protection scheme is designed to prevent the converter from being blocked due to overcurrent by protecting the high-speed outlet and the selective tripping of the DC circuit b...

AI Technical Summary

Problems solved by technology

The fault characteristics involved in the above method are related to the response of early faults under power frequency voltage or current excitation, so it is difficult to apply in DC scenarios, and the early fault characteristics are weak, making it difficult to determine the threshold of fault identification criteria

The research on identifying and locating early faults in DC scenarios is still immature, mainly using external parallel capacitors and peripheral high-frequency injection sources to realize early fault identification and locating; this type of active injection method has high reliability, but the disadvantage lies in the need Install additional equipment

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